Overnight ratings for NBC show almost 6 million people watched Leno return to his old home. CBS’ The Late Show With David Letterman brought in 3.3 million viewers. This is a big blow to Letterman who soared to the top of the late night ratings during Conan O’Brien’s term. And, this is The Tonight Show’s best overnight performance since Conan took over the Tonight Show on June 1, 2009.